The Law of One in history?

[3D Sunset]

So in summary my question is, what other pre-1981 (or how about pre-L/L Research) entities (via mediumship, etc), or religions gave us the core philosophy that all is one, if any?

I believe that if you look at different religions (particularly the mystic side of them) it will be harder to find a religion that does not have that as a core tenet. Here are a few that I selected from various sources across the web:

Hinduism :

Hinduism is both polytheistic, and pantheistic. There are three gods that compose Brahman – Brahma, Vishnu, and Shiva. Hindus also worship the “wives” of Shiva, such as Kali, or one of Vishnu’s ten incarnations (avatars). This is only the beginning. There are literally millions of Hindu gods and goddesses – by some counts, as many as 330 million!

At the same time, Hinduism teaches that all living things are Brahman in their core. In other words, all living things are Brahman, or god. Enlightenment is attained by becoming tuned in to the Brahman within. Only then can one reach Nirvana.

Christianity:

Jesus proclaimed "I and the Father are one," showing the world what the union of God and man can be. Christian mysticism is about nothing else but this transforming union.

Christ is the sole end of Christian mysticism. Whereas all Christians have Christ, call on Christ, and can (or should) know Christ, the goal for the Christian mystic is to become Christ—to become as fully permeated with God as Christ is, thus becoming like him, fully human, and by the grace of God, also fully divine. In Christian teaching this doctrine is known by various names—theosis, divinization, deification, and transforming union.

A common misconception about mysticism is that it's about "mystical experiences," and there are many volumes on such experiences in religious literature. But true mysticism is not focussed on "experiences" (which come and go) but with the lasting experience of God, leading to the transformation of the believer into union with God.

Muslim

I'm sure that Ali Quadir can give you many more relevant quotes here, but this came to mind.

O mankind! We created you from a single soul, male and female, and made you into nations and tribes, so that you may come to know one another. Truly, the most honored of you in God's sight is the greatest of you in piety. God is All-Knowing, All-Aware". (Quran, 49:13)

Zoroastrianism

Ahura Mazda will ultimately prevail over evil Angra Mainyu / Ahriman (see below), at which point the universe will undergo a cosmic renovation and time will end (cf: Zoroastrian eschatology). In the final renovation, all of creation—even the souls of the dead that were initially banished to "darkness"—will be reunited in Ahura Mazda returning to life in the undead form. At the end of time a savior-figure [a Saoshyant] will bring about a final renovation of the world, and in which the dead will be revived.


Ancient Egypt

Questioner: Could you tell us something of your historical background and your contact with earlier races on this planet? Then we would have something to start with.

Ra: I am Ra. ...We are those of the Confederation who eleven thousand of your years ago came to two of your planetary cultures which were at that time closely in touch with the creation of the one Creator...We had no thought of their being disturbed, as these cultures were already closely aligned with an all-embracing belief in the live-ness or consciousness of all.

...We attempted to contact the rulers of the land to which we had come, that land which you call Egypt, or in some areas, the Holy Land. In the Eighteenth Dynasty, as it is known in your records of space/time distortions, we were able to contact a pharaoh, as you would call him. The man was small in life-experience on your plane and was a … what this instrument would call, Wanderer. Thus, this mind/body/spirit complex received our communication distortions and was able to blend his distortions with our own. This young entity had been given a vibratory complex of sound which vibrated in honor of a prosperous god, as this mind/body complex, which we call instrument for convenience, would call “Ammon.” The entity decided that this name, being in honor of one among many gods, was not acceptable for inclusion in his vibratory sound complex.

Thus, he changed his name to one which honored the sun disc. This distortion, called “Aten,” was a close distortion to our reality as we understand our own nature of mind/body/spirit complex distortion. However, it does not come totally into alignment with the intended teach/learning which was sent. This entity, Ikhnaton, became convinced that the vibration of One was the true spiritual vibration and thus decreed the Law of One.

However, this entity’s beliefs were accepted by very few. His priests gave lip service only, without the spiritual distortion towards seeking. The peoples continued in their beliefs. When this entity was no longer in this density, again the polarized beliefs in the many gods came into their own and continued so until the one known as Mohammed delivered the peoples into a more intelligible distortion of mind/body/spirit relationships.

There are hundreds if not thousands of other examples. I know that some of these may not specifically reference your idea that "all are one", but when they use terms like "will be reunited in [God]", it is certainly implied.

Love and Light,

3D Sunset